Synchronous rectifier.



G. H. KIGKLI GHTER. I SYNGHRONOUS RECTIFIER.

APPLIOATION FILED AUG. 25, 1909 1,123,307. Patented Jan.5,1915.

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' ive/1'06 WHMM-wo Patented Jan. 5, 191-5.

3 SHEETS-SHEET 2.

Witwuoea 0. H. KIGKLIGHTER.

SYNOHRONOUS RECTIFIER APPLICATION FILED, AUG. 25, 1909. 1,123,301 Patented Jan.5, 1915.

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6'] 62 (L wanton witnesses I al'l'ozucus UNITEDSTATES PATENT OFFICE.

cmuuass H. xrcxmenrnn, or imwnn'nmz', scorn CAROLINA.

"SYNoHRONOus RECTIFiER.

. Specification of Letters Patent.

' k 0, Application filed August 25, 1909. Serial No. 514,583.

To all whom it ma concern 'Be it known t at I, CHARLE's KIoK- me rrsn, acitijze'n of the United States", and

resident of New'berry, county ,of 'Newberry,

and State-of South Carolina, have invented certain new and useful Improvements in Synchronous Rectifiers, of which the following is a specification.

This invention relates to a method and apparatus forv rectifying polyphase alternate currents and has for its object the attainment of a method and apparatus where- ,by a polyphase alternating current may be converted into a direct current with sparkless commutation.

The 'method' broadly stated consists in. successively connecting'the separate phases of a polyphase supply circuit in serieswith the direct current workingc ircuit during those intervals in which the. electrom otive force developed in the connected phase is greater than in the other phases. As soon as the electromotive force drops so as to become equal to that in the next succeeding phase, the phase is disconnected from the workmg circuit and-the succeeding phase is connected thereto. At the instant of commutation when the electromotive forces in both phases are substantiallyjequal, theyv are connected in parallel. rangement sparking is avoided as the phases are fnever. short circuited.

The apparatus consists in a rect'fying commutator having segments and brushes for attaining the above'results. The commutator is driven in synchronism with the polyphase supply circuit and the brushes are spaced around the commutator and the segments are of such length that the separate phases are successively connected in series with the working circuit twice per cycle.

At the moment of commutation the succeeding phases are connected in parallel to the. working circuit, and the transfer from one phase to the next is made while the electromotive forces in the phases are substantially equal. This enables the current to be gradually shifted from the phase whose pressure -is falling to the succeeding phase whose pressure is rlsing and thus sparking is avoided. The brushes. are provided with mechanism whereby they may be shifted.-

This shifting mechanism comprises'a mannally controlled handle and an automatlc mechanism controlled -'bythe' current.

a 17 and 18.

By means of, this. ar-

eamed Jan.s',-1915.

"In" the drawings, Figure I isan elevation showing one form of this invention; Fig.2

is a simple diagram showing the electrical connections of one of the forms; Fig. 3 is a diagram showing the com lete. electrical connections; Figs. 4, 5 and diagrammatic view showing another form are diagrams illustrating the theory of operation; Fig. 7" 1s a section on the line 7-7, Fig. 1, showing the brush shifting mechariism; Fig. 8 is'a of commutator; Fig. 9 is a diagrammatic.

view showing a third form of -commutator;

Fig. 10 is a diagram'of the system using the commutator, shown in Fig. 9. I

Referring to the drawings, 1'5 designates a bed plate to which are bolted pedestals 16,-

ings in the pedestals and has mounted upon it the armature of the motor which receives .current from the polyphase supply mains 21. The field of the motor is excited in any A field frame 19 of an alternat- 111g current motor is cast integral with the pedestal 16. A shaft 20 is mounted in bearsuitable mariner and in this instance the.

field is shown as excited by current obtained from the rectifying commutator 22, the circuitbeing provided with the usual switch 22,

' Upon the shaft 20 are mounted slip rings a 23, which-are connected to segments 2* of 8 slip rings and are connected with the direct thecommutator. Brushes 23' bear upon the current working circuit 25. The polyphase supply circuit is designated at 29 and the primaries 29 of the step down transformer, are connected thereto. The primary windings of the polyphase transformer are shown in this case as connected in delta. The sec- :ondaries of the step down transformer are indicated at 26, 27 and 28. Separate connec tions .lead' from the secondaries to brushes ocated on the commutator The brushes which are connected to the secondary 26 are indicated at 26, the brushes which are connected to the secondary 27 are indicated at 27 and the brushes which are connected to the secondary 28 are indicated at 28% A brushes are properly adjusted the lamps will go out, the switch 30 can then be cld sed and direct currentcan be drawn from the working mains 25.

Referring/to Fig. 2 which shows a'simple diagram of the electrical connections, it will be seen that the secondaries 26, 27 and 28 are successively connected in series with the working circuit 25. The, secondaries are connected in series with the working circuit 25 at those intervals in which the electromotive force in the connected secondary is greater than that in the other'secorrdaries. As soon-as the electromotive force drops, the commutator disconnects that secondary from the working circuit and connects the secondarv of the succeeding phase thereto. Duringthe instant of commutation, the-secondaries of the two succeeding phases will be connected in parallel, and therefore the transfer of the working circuit to the successive phases will be gradual.

Figs. 4, 5 and 6 illustrate the theory of operation of the rectifier. Referring to said figures A, B and C designate sine waves of a three-phase alternating current. The solid lines show 'how the negative current is rectified. In Fig. 5 is illustrated the transition of the rectifier from one phase to another. a shows the point where the brushes of phase B make contact with the segments,- and b the point where the brushes of A break contact with the segments. .During this interval when the two phases are in parallel, the pressure of A is first a little higher than the pressure of B, then the pressures are equal at a point 0, and then the pressure of B is higherthan the pressure of A. A small cross current will tend to flow first one way and then the other, but this The correction may be made in various ways,-

as by the use of larger transformers, by retarding the rotary armature of the motor by one of the methods well understood in the art, or by shifting the brushes, as indicated in Fig. 6. In Fig. 6, connection with the phase B is made at a, while connection with phase A is broken at. b.

At the time of this break, the pressure in B'exceeds that in A by the amount cl, 6. This difference of pressure may be adjusted to shift all the current to B by the time contact with A is A broken, in which case there will be no spark- The adjustment may be manually controlled or automatically controlled. Figs. 1 and 7' show one form of adjustment. The brushes are mounted upon a brush holder 35.

. which is mounted for rotary movement upon pedestal with an arm 37 adapted to receive a threaded shaft 38 provided with a hand wheel. The lower end of this shaft extends into a hole in the lug and is provided with a circumferential groove adapted toreceive a set screw 39. By means of this construction the brush holder may be shifted manually by operating the hand wheel and the shaft 38,.and the set screw 39 provides a detachable connection between thehand wheel and the lug 86. In order that the lug may adjust itself to the shaft 38, this lug. is preferably pivoted on.one of the spokes of the brush holder 35. A lever 40 is pivoted at 11 upon the pedestal 18. This lever is connectedto the brush holder by means of links- 4:2,43. Asolenoid windingl is mounted upon the bed plate and a solenoid core 45 extends 46 being provided so as to cut out thissolenoid. The lever 40 is normally held in engagement with one of the stops 48 mounted upon the pedestal 18 by means of a spring 47. The upper stop represents the no load position of the brushes. A dashpot 49 mounted in the bed plate 15 is provided with a plunger 50 connected to the lever 40 to dampen it.

It will thus -be seen that the above con- 1 struction provides both a manually and an automatically controlled mechanism for controlling the position of the brushes. If the variation in the current taken from the rectifier is gradual, or if the current :is constant for large periods and the variation may be determinedin advance, the manually controlled mechanism maybe used for shifting the brushes. However if the variation of current is rapid,, as .in the case where the load is composed of motors which are frequently' started and stopped, it is preferable to use the automatically controlled mechanism. Either may be used at will by connecting'or disconnecting the shaft 38 from the lug 36 and by opening and closing the switch 46. 4 i r In-a rectifier of two segments one revolutionper'cycle is sufficient but the rectifier can be operated .at justone-half or onethird speed with the same number of brushes by interconnecting the collecting segments of like potential in any suitable manner. Fig. 8 shows such a connection. The numbers 26", 27 and 28", 26, 27 and 28 show all possible positions of the brushes. It is evident that the dotted brushes can be omitted and that-remaining brushes 26", 27 and 28 can collect the current. In this construction the arcs spanned by the segments i 24' are just one-half of that shown in Fig. 2. The opposite segments are intercon- '-nected, as shown.

By this construction a slower speed of the rectifier. may be employed,w hile the number 'of brushes is not increased, and these brushes are distributed around the rectifier commutator in such a way as to avoid crowding.

Figs. 9 and 10 show another form in which the secondaries are connected to slip rings electrically connected to the commutator segments, While the direct current is taken off by a pair of brushes resting on they commutator. In this form 51 designates the, polyphase supply circuit having connected thereto the primaries 52 ,ofthe polyphase transformer, the transformer windings being connected in delta. The secondaries of the step down transformer are designated by 56, 57 and 58. The open secondaries of the transformers are connected to slip rings 60 mounted upon a shaft 20, which slip rings are connected-to the commutator segments. Intracing out the connections, it will be seen that the secondary 56 is connected to the segments 56, the secondary 57 to the segments 57, and the secondary 58 to the segments 58. The current is collected from the commutator by means of brushes 61 connected to the terminals of the direct current working circuit designated by (S2, 62.

It will be noted that the segments con nected to the successive phases overlap and thus the operation of this rectifier will be the same as in the construction shown in Figs. 2 and 3, that is, the separate secondaries will be successively connected.in series Withthe direct current working circuit and during the transfer of the direct current circuit from one phase to another, two

phases will be connected in parallel.

The alternating current motor which drives the rectifier" is preferably of the synchronous type and is preferably pro- -vided with devices for preventing hunting.

These devices are Well known to those skilled in the art and consist in copper bridges or squirrel cage'windings located in the field poles.

In order to obtain good results, the'length of the arc spanned by the segment issubsor of the same; in a five-phase 36 oi a. di

visor of the same; in a six-phase 30 or a divisor of the same and so 'on. By increas- 'ing' the are spanned by the segments ofthe rectifier the time during which the'two secondaries are in parallel may be increased until the period when one alone is in circuit is reduced to zero and there are always'two ,in parallel and even at times three. But the inotive force drops to the value of the suc-.

ceeding phase it is disconnected from the working circuit and the next phase con} nected. The transfer is made gradually and without short circuiting the secondary which is connected .or disconnected. By thus separately and successively connecting the separate phases to the working circuit, the cross currents between the phases, which occur'in" the case where all the phases are connected in series witha direct current working circuit at all times, are avoided.

In the specific type described, the invention 'is shown as applied to a three-phase system. It is obvious, however," that this invention may be applied to po'lyphase sysis to be therefore understood that this inventems' other than three-phase systems and it tion is not to belimited to a three-phase system. It is'further obvious that various changes may be made in the details of construction it without departing from the spirit of this invention, and it is therefore to be understood that this invention is not to be limited to the specific construction shown and described.

' Having described mv invention what I claim and desire to secure 'by Letters-Patcut is. v

'1. The combination with a-- three phase stant-ially equal to one-half of the angleot supply circuit the individual phases o'fwhich displacement of the phases or a divisor of the same, as shown in Fig. 8, where a number of segments are interconnected. Similarly the arc spanned by adjacent brushes is also, substantially equal to one-half of the angle of displacement of the phases or a divisor of the same. Thus in a three-phase rectifier the angle of displacement of the brushes or the arc spanned by the segments ,,will be substantially 60 or a di isor of the same;.in a four-phase rectifier 45 or a. divihave separate terminals, of a direct current time of tra'ns'fer, said rectifier being arr-- ranged to connect each phase to the working circuitwhile the electromotive force in each p'has'e is at amaxlmum andbefore the preceding one is disconnected therefrom and at that. time "at which the'electromotive force developed in the phase which is connected is of slightly greater value than in the preceding phase which is disconnected, the said rectifier being adapted to connect the two succeeding phases' iin, parallel to the working circuit at the time'of transfer and means for varying'fthe adjustment of said segments and -brushes'. I

2. The combination of a polyphase supply circuit. a transformer connected thereto and,

including a secondary winding the phasesof which are separate and provided with independent terminals, a direct current workf ing circuit, a rectifier arrangedto be driven 1n synehronism 'wlth the suppi'y circuit and provided with a set of segments and a set of brushes, the an ular displacement of the members of one 0% tially a divisor of'one-half of the angular displacement between the phases of the supply circuit, and non-adjacent members forming a pair and being connected to and in the same circuit, connections from the separate phases of the secondary winding to the circuit at th members of one of said sets and' other connections from the 'Working circuitto the members of theothe'r of said sets.

3. The combination of a' three phase supplycircuit, a transformer connected thereto and-including a'secondary winding the phases of which are independent and have separate terminals,a direct current working circuit, means for/successively and individually connecting the separate phases of said secondary winding'in series with the working circuit and adapted to preventshort circuiting of the phases'at the time oftransfer, said means being arranged to connect each phase to the working circuit before the preceding phase is disconnected therefrom and at that time at which the electromotive force developed .in the-phase which is con; nected is slightly greater than in the preceding phase which is disconnected, the means being adapted to connect the two succeeding ph ses in parallel to theworking t time of transfer and means for varying the adjustmentof said connecting means comprising a manually operable shifting member and an automatically operable;

shifting member, either of said shifting members being adapted to be set in operation atwill.

4. The combination of a polyphase supply circuit, a transformer ,having its primary winding connected to said polyphase circuit, the secondary of said transformer comprising separate phases having separate pairs of leads. two three-pole switches, one

of each of said pairs of-leads being 'conn'ect ed to the first three-pole switch, the other of said sets being substaneach of said pairs of leads being connected to the second three-pole switch, a commutator rotatable in synchronism with said poly phase supply, a direct current working circuit, a set of segments on said commutator to which the working circuit is connected,

pairs of brushes adapted to bear on the segments of the commutator, the brushes comprising each pair being located on opposite sides of said commutator and connected to corresponding poles of saidtwo three-pole switches,,a device connected to each pair of brushes and in shunt circuit around one-of said switches to one of each of the leads of said secondary phases and arranged to indicate when the ad ustment of the brushes is such that the cross currents between the sgcondary phases is substantially zero, said' commutator through said segments and brushes being adapted to successively and individually connect the separate secondary power thereto when said switches are closed, each of said secondary phases being connected to the working circuit before the preceding one is disconnected therefrom'and while the electromotive force developed therein is a maximum, two succeeding phases being connected in parallel to the workingcircuit at the time of transfer, and means for adjusting the relative position of the segment and brushes comprising a manually operable shifting member and an automatically operphases to the working circuit to supply able shifting member, either of said shift ing members being adapted to be set in operation at will. i

5. ,The combination of a polyphase supconnected in series with theworking circuit I twice per cycle. g w

6. The combination of a polyphase supply circuit, a transformer, the phases of its pri- 'mary winding connected in delta to said supply circuit, the phases of the secondary winding of said transformer being separate and having separate pairs of leads, two separate three-pole switches, oneilead of each of the pairsof secondary leads being connected to one pole of one of said switches and the other lead of each pair being connected to a pole of the other switch, a direct current 'working circuih-a cqnimutator rotating in 'synchronism with gsaid supply circuit and having the segments thereof connected with said direct current working circuit, pairs of brushes bearing on and s bace& erolm. said commutator. the brushes comprising a pain-1 nected in shunt around the poles of one of said switches to indicate when the adjust ment of the brushes is such fleet the cross current between the phases is substantially zero. Y

7 The combination of e polypha'se supply circuit, a transformer, the phases of its primary inding connected in delta to said supply circuit, the phases of the secondary winding of said transformer being separate and. having separate pairs of leads, two sep-l crate three-pole switches, one leacl of each of the pairs of secondary leads being connected to one pole of one of said swieches and the other lead of each pair being connected toe pole of the other switch, a direct currem;

working circuit, a commutetor'xotefiieginsyii'chronism with sei supeiy circuit aria having the segments ehere'efi connected with said direct current workieg circuit, pairs oi brushes bearing on and spewgi ag-ound said commutator, (she brushes comprisinge peir,

being located on opposite sides cf the co'm- .muisetor and connecte ;.cor 'e'sponding poles of the tweswiiiches, means connected in shunt around: theflpoles' of one of sand switches to imlicetewhecflm adjustment of the brushes is such that the cross current bf tween the phases is substantially zero and means for shifting the brushes comprising a tion-atwilk'yi I I In testimony whereof I afmy-szgn'eture in presence of two Witnesses. v QHARLES H. KICKHGHTE-Bc Winesses: I 1 Y R, 8. Eve, R. P. Peon 35 I manuall device and "en :mto'nmtie device," either of which is adapted to The set 1319136178? Qcpice ofi skis eaten may cs ei teieee'fier five enteeaeh hy efiiressiiigl she matches e2 Eetegge i Wesi iagtce, E. 5., v 

